1. Field of the Invention
The present invention relates to new pyridazinone derivatives possessing useful pharmacological activities and to processes for preparing the same. More particularly, the present invention relates to new 6-(substituted phenyl)-4,5-dihydro-3(2H)-pyridazinone compounds having strong platelet aggregation inhibiting activity and blood pressure depressing activity and to processes for the preparation of such new pyridazinone compounds.
2. Description of the Prior Art
Certain kinds of dihydropyridazinone derivatives are known to possess useful pharmacological activities. For example, the 6-(p-acylaminophenyl)-4,5-dihydropyridazinone-(3) compounds disclosed in Japanese Laid-Open Patent Application No. 54-9289 are reported to possess platelet aggregation inhibiting activity as well as blood pressure depressing activity. A number of studies are still being conducted to investigate useful pharmacological activities of various pyridazinone derivatives. Under such circumstances, there is a great demand in this art for developing additional new classes of pyridazinone derivatives having valuable pharmacological activities.